Multiple deployments, Multiple projects in a Visual Studio solution

We use Bitbucket and Bamboo. We have a Visual Studio solution that has about 20 projects in it. Out of 20 projects there are about 10 projects that need to be built and deployed either as windows services or web apps in IIS. We have individual solutions for these 10 components. There are shared components across these 10 components. For example, there is a contracts project which is shared by Order and Inventory service. So, any change to contracts project should trigger build of Order and Inventory but not others. We want to go with one repository because of branching requirements of git flow. It will be too much of effort to maintain 10 repositories for each of deployable component. The question is how to configure build triggers?